Her daughter, Karissa, who is in year 8 at Catherine McAuley and has dyslexia, will "never have the chance" to pass the tests, Dr Piller said.

"We have definitely started looking at how different states treat students with disabilities and we're seriously looking at moving because you want to give your kids the best options and it's hard to justify taking all of those away," said Dr Piller, a senior lecturer at Western Sydney University's school of science and health.

After school on Wednesday, Karissa travelled to the city from Westmead with her mum to join dozens of other students and parents outside Parliament House to protest the changes to the Higher School Certificate.

"I want to work with animals when I finish school and I want to go to uni or at least have the chance to," Karissa said.

"I'm worried and a lot of my friends are worried they won't ever pass."

Another group of year 9 students from the International Grammar School said they did well in the NAPLAN tests but thought the policy was "unfair".

"If you're not the most academic, that doesn't mean you're worth less or your future is worth less," Allegra Welsh, 15, said.

Martine Beaumont, founder of the HSC, Opportunity, Potential for Everyone group, which organised the protest, said she and other parents have been seeking a meeting with Education Minister Rob Stokes and Department of Education secretary Mark Scott over the issue.

"We're here because we're not being listened to, kids want to have a voice, parents want to have a voice," Ms Beaumont said.

Under the new policy, which was announced in July last year, students who are currently in year 9 will be required to meet a minimum literacy and numeracy standard by achieving band 8s in their NAPLAN reading, writing and numeracy tests or passing online tests in subsequent years in order to get their HSC.

Mr Stokes said that he has "yet to hear a good reason why we shouldn't expect students to have basic level of literacy and numeracy when they leave school".

"We have introduced the HSC reforms to raise standards for our students leaving school to make sure they have a minimum standard of literacy and numeracy, to motivate them and challenge them to achieve at the highest possible level, and to prepare them as well as possible for life after school," Mr Stokes said.

However, Labor's spokesman for education Jihad Dib said that "the fact that so many people and so many students are out here shows how important this decision is".

"Contrary to what the minister thinks, the general public do not think this is a good idea. I'm all about raising standards but anyone who knows anything about education says this is not the right way to do this," Mr Dib said.

Dr Piller said Karissa wants to keep studying after school but probably won't get the chance to do so without the HSC credential.

"The HSC in itself already tests that in a way that lets students fulfil their potential in different areas," Dr Piller said.

"You don't have to be good at both English and maths. Combining the two just cuts out a lot of people who could pursue further education in areas that are important to society.

"Karissa's not stupid but she will never achieve the band 8 [in next year's NAPLAN tests]. And it puts even more pressure on them if they can sit the online tests [in later years], and they probably still won't get it."